Field of the Invention
The present invention relates to a sheet stacking apparatus in which a sheet is stacked and to an image forming apparatus having the sheet stacking apparatus.
Description of the Related Art
The maximum length of a sheet which a user uses in a sheet conveying direction was previously about 19 inches. However, the demand for a sheet which is called “a long sheet” with a length of 26 to 30 inches (=660.4 to 762 mm) has been increasing as diversification progresses. In a case where such a sheet is used, when the length of a stacking tray is much less than the length of the sheet, the sheet may fall from the stacking tray. Thus, in order to stack a long sheet with the length of 30 inches, it is necessary for the stacking tray to have the length of about 30 inches.
On the other hand, since a user of a long sheet does not always use a long sheet, it is wasteful that the tray with the length of 30 inches occupies a user area. Thus, it is desirable that an extension tray for a long sheet has such a configuration that the extension tray can be detached or stored by a user and the extension tray can be used only when necessary.
For this reason, an extension tray for stacking discharged sheets that is provided in a detachably attachable manner has been proposed. In the configuration of such an extension tray, a leg portion for attachment is provided on a paper supporter made of a wire member and is configured to be inserted into a sheet discharging portion of an electronic device (Japanese Patent Laid-Open Application No. H9-278259).
When the extension tray is configured to be detachably attachable, it is desirable for the extension tray to be easily attached or detached. However, when the extension tray is configured to be easily attached or detached, a problem occurs in which the extension tray may unexpectedly come off.
On the other hand, when the extension tray is configured not to unexpectedly come off after having been attached, the operability of attaching and detaching of the extension tray becomes low.